Immigration authorities last week arrested 680 people who were in the United States illegally, Homeland Security Secretary John F. Kelly said in a statement Monday.

The raids in at least a dozen states, which marked the Trump administration’s first large-scale crackdown on people living in the United States illegally, set off a wave of panic and protest in immigrant communities over the weekend and sparked questions from immigration advocates as to whether the arrestees posed legitimate threats to public safety.

DHS, which overseas U.S. Immigration and Customs Enforcement (ICE), said Monday that approximately 75 percent of those arrested were “criminal aliens,” including some who had been convicted of crimes such as homicide, sexual assault of a minor and drug trafficking.

Asked to provide further clarification, a DHS official confirmed that the term “criminal aliens” includes anyone who had entered the United States illegally or overstayed or violated the terms of a visa. There are an estimated 11 million people in the United States who fit that profile.

ICE declined to provide the names and locations of those who were detained in the raids, nor would the agency say how many of the 680 people had committed serious crimes.

Field offices in Los Angeles, San Antonio, Chicago, Atlanta and New York City released a total of 15 examples of people ICE took into custody last week, including one who was a “self-admitted MS-13 gang member” and one who was wanted for murder and attempted murder in Mexico. Seven had prior convictions for sexual assault or for lewd or indecent acts with a child, and three, including the gang member, had convictions for drug trafficking or distribution.

ICE carried out the arrests in New York, California, Illinois, Texas, Missouri, Kansas, Georgia, North Carolina, South Carolina, Kentucky, Indiana and Wisconsin. Of those, about a quarter had no prior convictions.

ICE has characterized the raids as routine, but immigrant rights groups said the actions were out of the ordinary and that most of those swept up were not dangerous. They said ICE also handled the detentions — which activists described as playing out in homes, on the side of the road and outside workplaces — differently from how the agency had in the latter years of the Obama administration, and accused the government of sowing fear among the immigrant ­community.

“This is not normal,” Sulma Arias, field director for the Center for Community Change, said in a teleconference with reporters Monday, calling it a “horrific overreach that will destroy families and undermine the American Dream for thousands.”

The Center for Migration Studies of New York, a think tank that favors immigration, says there are about 3.3 million households in the United States that contain both legal and illegal residents. Most of those homes have U.S. citizens, including 5.7 million ­U.S.-born children.

Obama, who deported more people than any president, in his second term prioritized deportations to target public safety threats over other people with less-serious criminal violations.

More than 90 percent of those deported from the United States during the past fiscal year had been convicted of what DHS considers serious crimes, according to a Migration Policy Institute study. Activists say ICE also tended to detain people at night, which was often terrifying but less public.

“The Obama administration shied away from big displays of enforcement because it would alienate their base. For Trump, it is red meat for his supporters and fulfills a campaign pledge,” said J. Kevin Appleby, senior director of international migration policy for the Center for Migration ­Studies of New York.

Thousands of immigrants and activists rallied outside the Milwaukee County courthouse in Wisconsin on Monday for a “Day Without Latinos, Immigrants and Refugees.” The event was designed to demonstrate how integral the groups are to the nation’s social and economic fabric.

abigail.hauslohner@washpost.comsandhya.somashekhar@washpost.com

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